She may be getting cold, hot, hungry, lonely, etc..there may even be the same car or motorcycle driving down the street at the same time every morning.
I would make sure she has a good snack about half an hour before bed, limit any foods or drinks that have any caffeine in them during the last half of the day, make sure she has the proper amount of blankets, then tell her she is welcome to come get in bed with you. At least that way the boy can sleep through the night. She will come to you and then you'll be the only other one woke up.
She is just growing and maybe not needing as much sleep. You could also try moving her bedtime back half an hour or more. She may just not need any more sleep past that time. I'd much rather have some one sleep a little later than have them waking every morning so early.